A Montgomery County teacher who sued a parent for $1 million after she complained about his teaching and coaching practices dropped his lawsuit this week after feeling symptoms of a heart attack just as he was to take the witness stand.

Paul Hassler, a math teacher at Rockville's Magruder High School, felt chest pains and began sweating profusely Wednesday, the second day of a jury trial in his defamation suit against Suzanne Sutton, his attorney, Charles S. Rand, said yesterday.

Rand drove the teacher to the Shady Grove Hospital emergency room, where he underwent tests before being transferred to Holy Cross Hospital. Hassler, who was released from Holy Cross yesterday after passing a stress test there, said he had a heart attack and triple-bypass surgery in 1993 and has had more heart problems since.

The chest pains brought a sudden end to an unusual lawsuit that raised questions about when a parent's complaints go too far and unfairly damage a teacher's reputation.

Hassler was believed to be the first teacher to file such a lawsuit in Maryland, lawyers involved in the case said.

Courts in seven other states have granted parents immunity from such claims.

Those courts have ruled that parents should not be dissuaded from complaining about their children's teachers, said Sutton's attorney, Joseph Suntum.

Hassler alleged that Sutton's four-page complaint to his principal and five of the principal's superiors was untrue, malicious and designed to ruin his 30-year career.

In the letter, Sutton, who works as a private math tutor, wrote that Hassler had humiliated students by berating them in public and telling off-color jokes.

She also complained that he told players on the varsity softball team to lie about their participation in an illegal preseason softball clinic and rewarded his athletes with good grades in math class.

Sutton, of Derwood, argued in court that she was being unfairly penalized for telling school officials about long-running complaints she had heard from her daughter, who has since graduated, and other Magruder math students and athletes.

She said she put her complaints in writing because the Magruder High principal told her to and that they were never fully investigated.

Hassler won't be allowed to refile his lawsuit. Montgomery Circuit Judge Durke G. Thompson ruled in favor of Sutton by finding that Hassler had not proved his case before ending it.

"It wasn't worth ending my life or becoming permanently disabled over," Hassler said. "I'm sorry I couldn't go on because so many teachers were behind me and thanking me."

Sutton said she also was disappointed: "I've been called a liar by Mr. Hassler for over a year. . . . The man who brought the suit pulled out before he had to testify. I wanted to establish the truth."

The question of when parents' complaints spill over into defamation may yet reach a Maryland courtroom.

Another Montgomery high school teacher filed a similar lawsuit several months after Hassler.

Christopher A. Flynn, a former track coach at Walt Whitman High School in Bethesda, sued several parents after he was transferred and lost his coaching job.

He blamed their complaints that he had sexually discriminated against their daughters on the school's cross-country team.

Thompson dismissed that case in June, saying such lawsuits could discourage children from reporting improprieties, but the teacher has appealed that decision.